Only time will tell - but from my first impressions and testing recently, I LOVE IT!
I installed Microsoft Security Essentials Beta and it worked brilliantly a while ago, very low memory footprint, small size e.t.c.... I have become less impressed with Nod32 recently (they are going down the Symantec trap - money in advertising and not product development), Anyway, I thought it was fast and did the job.
However, I upgraded my pc a few months ago and I have not been using any AV (I have Windows 7, UAC on maxmium, and I never install programs that I do not know / used in the past), and generally been very happy. However, If you must have an AV solution, I would seriously consider this if you do not need central management / enterprise AV.